The present invention relates to a sprayable filler composition, and more particularly, to a high solids, low-volatiles sprayable filler composition which may be used as a coating on a variety of substrates, and which provides a corrosion resistant, sandable surface.
Multi-component spraying systems are widely used in the plastics and marine industries. In such systems, a liquid resin and a catalyst for the resin are mixed together and sprayed onto a substrate such that the catalyst and resin react and harden on the substrate. The mixing may be done immediately before spraying (referred to as an internal mix system) or immediately after spraying (referred to as an external mix system). In either event, such coatings are referred to as a "gel coat". For example, U.S. Pat. No. 4,967,956 to Mansfield discloses a "gel coat" spraying system which uses a resin such as an epoxy resin or a polyester resin, a catalyst for the resin, and spraying means which includes an airless liquid nozzle. Such gel coats utilize a slow curing process, and the coatings do not provide a sandable surface.
Another disadvantage of such gel coatings is that application of the coatings is effected through the use of organic solvents to reduce viscosity. Because of increased environmental concerns about volatile organic components (VOC's), efforts have been made to reduce the amount of volatile materials used in such coating operations. As a result, the use of high solids coatings has been employed to meet VOC regulations. For example, White et al, U.S. Pat. No. 5,057,555, discloses a coating composition having a high solids content which is used as a finish for automobiles and trucks comprising an acrylic polymer and a catalyst. However, the coating cures very slowly. In addition, the composition still includes from 20-60% of an organic solvent. Further, such high solids coatings often run and sag when applied to vertical surfaces, and they have poor shelf and pot life.
As an alternative to using organic solvents, Bok et al, U.S. Pat. No. 5,171,613, teaches using a supercritical fluid as a non-polluting diluent in combination with a coating mixture. However, the method of spraying the coating requires the use of a heated spray gun to maintain the temperature of the coating mixture.
Accordingly, there is still a need in the art for a sprayable coating composition which may be easily applied to a variety of substrates, cures quickly, provides a sandable surface, and contains low volatiles.